In the related art, a motor in which a conductor divided into a plurality of segments (a so-called SC winding: a segment conductor winding) is inserted into a slot to cover the slot with no gap according to a shape of the slot is known as a motor having a stator having a slot in which a winding is inserted. In the motor, because a space factor of the winding in the slot is increased, it is difficult to easily detect a winding temperature in the slot, and the winding temperature in the slot may be indirectly estimated from a winding temperature detected at a coil end or the like outside the slot. However, since heat generation is increased due to an increase in a space factor of the winding, cooling of the winding by a coolant at the coil end or the like outside the slot may be performed, and thus, it may be difficult to precisely estimate the winding temperature in the slot from the winding temperature outside the slot.
With respect to the occurrence of such a problem, in the related art, a technology in which temperature dependency of each of a winding resistance value and a winding inductance of a motor is linear, and a winding temperature is estimated using a voltage equation of the motor is known (for example, see Patent Document 1).
In addition, in the related art, in a case in which the winding temperature of the motor gets high during a restart of an operation due to turning on an ignition switch of a vehicle, a temperature estimation device using a temperature difference between the surrounding temperature of the winding and a temperature estimation value based on the winding resistance as an initial value of a temperature increase estimation value is known (for example, see Patent Document 2).